Sender Policy Framework (SPF) is method used identify where email sent on your behalf is allowed to originate from. It works on the envelope from address (also known as the return-path or bounce address) and not the header from address which is typically visible to recipients.
SPF records are stored as DNS records in the domain being protected and detail the email servers and computer networks which are authorised to send email on behalf of the domain name.
Just having an SPF record will give your deliverability a lift, especially if you are a bulk sender. Not having one can hurt deliverability.
So, even if you are not engaged in email marketing, it’s a good idea to set up SPF for your domain.